1. Field of the Invention
The present invention relates generally to a method of minimizing noise perception in a motor vehicle, and in particular to a method of masking the noise attributable to the battery cooling system of a hybrid electric vehicle.
2. Background Art
Governmental regulations and environmental concerns have dictated the need for automobile manufacturers to develop more fuel efficient power trains. All-electric and hybrid electric powertrains are two examples of such powertrains currently under development. Although all electric vehicles are desirable in that such vehicles offer the potential to be simply regenerated by plugging into a power outlet and may completely eliminate fossil fuel dependence, even after many years of research these vehicles are currently limited by current technology and only have a limited distance range. Hybrid electric vehicles possess increased fuel economy by combining the functionality of electric vehicles with internal combustion vehicles.
Hybrid electric vehicles (“HEVs”) combine an internal combustion engine or some other primary source such as a fuel cell system with a secondary power source such as a high powered battery and electric motor. This dual powering mechanism allows HEVs to have extended range and similar refueling to fossil fuel vehicles. Presently, batteries are only able to store enough energy for short trips. Therefore, the inclusion of an internal combustion engine in HEVs allows an onboard generator to recharge the battery and to be used as a power source to run the electric engine. This combination not only leads to increased energy savings but also a decrease in undesirable automobile emissions.
There are currently various designs for hybrid electric vehicles. However, HEVs generally include primary and secondary power sources, a mechanism to propel the vehicle, and one or more energy storage devices. Power sources include internal combustion engines, gas turbines, and fuel cells. Electric motors are one type of mechanism used to propel HEVs and may be combined with a variety of transmission mechanisms, such as, planetary gear sets, CVTs, and other gearing for delivering tractive force to the vehicle's driveline. Although batteries are the most common storage devices, alternatives including ultracapacitors are possible.
The high powered batteries which are presently used tend to be quite large and bulky requiring cooling because of the high current drawn to propel a vehicle. Typically, the high powered batteries are kept cool by fans. These fans tend to produce an excessive amount of undesirable noise.
Accordingly, there exists a need for improvements in hybrid electric vehicle design. In particular, there is a need for control strategies that minimize the levels of drive-perceptible NVH attributable to battery cooling.